Effect of heat shock response on the cleavage of nucleolin induced by oxidative stress

Objective: To observe the cleavage of nucleolin (C23) during apoptosis induced by oxidative stress and to clarify the effect of heat shock response (HSR) on the cleavage of nucleolin and its possible molecular mechanism. Methods: We added 0. 5 mmol/L peroxide hydrogen (H ₂O ₂) into cultured cells to mimic oxidative stress. Apoptosis and cleavage of C23 were detected using caspase-3 colorimetric assay and Western blotting respectively. HSR was performed to observe the effect of HSR on cleavage of C23 induced by oxidative stress, and overexpressions of HSP70 and HSP25 were detected by Western blotting. Results: Activity of caspase-3 increased significantly after 2 hours of 0. 5 mmol/L H ₂O ₂treatment, and reached the peak after 12 hours. The cleavage of C23 appeared 30 minutes to 1 hour after the treatment of H ₂O ₂ as indicated by a cleaved fragmentation of 80 kD, which was significantly inhibited by HSR. Moreover, HSR could induce HSP70 and HSP25 overexpressions. Conclusion: Oxidative stress can induce the activation of caspase -3, cleavage of C23, and apoptosis. HSR can significantly inhibit the cleavage of C23 induced by oxidative stress, which is related to the overexpressions of HSP70, HSP25, and other stress proteins.